A MySQL database, like all other types of databases, is used to keep track of a website or software's data.
The technical term for MySQL is a relational database management system, or RDBMS. MySQL is a software program that runs at all times on a server and gives other programs access to the information it maintains.
This information is stored in databases. A database is made up of tables. Each table is structured into fields that can contain a specific type of information; some fields can contain only numbers, while others can only contain dates, etc.
When data is inserted into a table, each group of fields is called a row.
MySQL controls access to this information with usernames and passwords, just like when you log in to a computer. Each username gets permission to do certain things with certain databases.
You can create MySQL databases, users, and passwords inside your control panel.
If you plan to install web software on your hosting account, you'll need at least one MySQL database. Most web software is designed to share a single database with more than one other software program.
You'll also need to create a username and password for the software to use. Be sure to make the password as complex as possible, because it's not a password you're going to need to remember. Usually, a program will store its MySQL password in a configuration file; you'll never need the password again after installation.